How Do Microphysical Processes Influence Large-Scale Precipitation Variability and Extremes?

TitleHow Do Microphysical Processes Influence Large-Scale Precipitation Variability and Extremes?
Publication TypeJournal Article
Year of Publication2018
JournalGeophysical Research Letters
Volume45
Number3
Pages1661-1667
Date Published04/2018
Abstract / Summary

Convection permitting simulations using the Model for Prediction Across Scales‐Atmosphere (MPAS‐A) are used to examine how microphysical processes affect large‐scale precipitation variability and extremes. An episode of the Madden‐Julian Oscillation is simulated using MPAS‐A with a refined region at 4‐km grid spacing over the Indian Ocean. It is shown that cloud microphysical processes regulate the precipitable water (PW) statistics. Because of the non‐linear relationship between precipitation and PW, PW exceeding a certain critical value (PWcr) contributes disproportionately to precipitation variability. However, the frequency of PW exceeding PWcr decreases rapidly with PW, so changes in microphysical processes that shift the column PW statistics relative to PWcr even slightly have large impacts on precipitation variability. Furthermore, precipitation variance and extreme precipitation frequency are approximately linearly related to the difference between the mean and critical PW values. Thus observed precipitation statistics could be used to directly constrain model microphysical parameters as this study demonstrates using radar observations from DYNAMO field campaign.

URLhttp://dx.doi.org/10.1002/2017gl076375
DOI10.1002/2017gl076375
Journal: Geophysical Research Letters
Year of Publication: 2018
Volume: 45
Number: 3
Pages: 1661-1667
Date Published: 04/2018

Convection permitting simulations using the Model for Prediction Across Scales‐Atmosphere (MPAS‐A) are used to examine how microphysical processes affect large‐scale precipitation variability and extremes. An episode of the Madden‐Julian Oscillation is simulated using MPAS‐A with a refined region at 4‐km grid spacing over the Indian Ocean. It is shown that cloud microphysical processes regulate the precipitable water (PW) statistics. Because of the non‐linear relationship between precipitation and PW, PW exceeding a certain critical value (PWcr) contributes disproportionately to precipitation variability. However, the frequency of PW exceeding PWcr decreases rapidly with PW, so changes in microphysical processes that shift the column PW statistics relative to PWcr even slightly have large impacts on precipitation variability. Furthermore, precipitation variance and extreme precipitation frequency are approximately linearly related to the difference between the mean and critical PW values. Thus observed precipitation statistics could be used to directly constrain model microphysical parameters as this study demonstrates using radar observations from DYNAMO field campaign.

DOI: 10.1002/2017gl076375
Citation:
Hagos, S, L Ruby Leung, C Zhao, Z Feng, and K Sakaguchi.  2018.  "How Do Microphysical Processes Influence Large-Scale Precipitation Variability and Extremes?"  Geophysical Research Letters 45(3): 1661-1667.  https://doi.org/10.1002/2017gl076375.